Part of the beauty of Jupiter’s icy moon Europa is its incredible smoothness. But like most things, if you look closely, cracks appear in this facade. In Europa’s case, the cracks come in the form of jumbled pieces of ice that make up what are called the moon's “chaos terrains.” Just what caused the chaos is an open question.

There is, however, an obvious candidate. Europa’s most exciting characteristic is probably the ocean of liquid water that is thought to exist beneath that icy crust. It seems likely that the ocean has something to do with the chaos terrain, especially given the presence of salt there. To figure that out, however, we’d have to know something about how water circulates in that ocean. And, unlike our own oceans, you can’t just chuck a buoy in and see where it goes.

Circulation in the ocean would be driven by the heat from Europa’s interior. It’s been thought that the big-picture pattern might look something like the atmosphere of Jupiter, with alternating bands of eastward or westward flow. Ultimately, this pattern carries the greatest amount of internal heat to Europa’s polar regions. A new study, led by University of Texas at Austin researcher Krista Soderlund, suggests the circulation pattern could actually look quite different.

The researchers created a mathematical model of Europa’s ocean that could simulate the Jupiter-like circulation pattern. Then, they played with a key parameter in the equations—a term known as the Rossby number. It has to do with how strongly the Coriolis effect—the force that causes air to spiral in toward the low pressure at the center of a hurricane—influences the flow of the ocean water.

Estimates for what value of the Rossby number best represents the conditions on Europa have varied, but only the smaller values produce a Jupiter-like circulation pattern. By using a larger value in their model, the researchers push the circulation pattern into a very different configuration.

The flow is a little more complex, and the neatly separated bands of eastward and westward flow break down. It’s a little less Jupiter-like and a little more like Earth’s atmosphere. On Earth, a convection cell in the tropics carries air upwards at the equator and back down around 30 degrees north and south latitude. That same kind of behavior shows up in the ocean in this model, with a Coriolis-induced westward component to the flow, just like the trade winds on Earth. At high latitudes, the simulated water flows in the opposite direction.

Most importantly, heat is distributed much differently. Rather than warming the poles most, warm water generally rises at the equator, with cool water sinking at the poles. That’s intriguing, because the chaos terrains mostly exist between 40 degrees south and north of Europa’s equator. If this picture of Europa’s circulation is accurate, it would seemingly link the delivery of heat to the underside of Europa’s icy shell near the equator, which could then lead to the unknown process that forms the chaos terrain.

In an accompanying article, Wheaton College astronomer Jason Goodman laments the difficulty of studying Europa’s intriguing subsurface. “If we hope to directly sample Europa’s ocean, traversing the last few kilometers of ice may prove a greater challenge than crossing a billion kilometers of interplanetary space. In the meantime, indirect observations and computer simulations continue to provide new insights into this mysterious alien ocean.”

The problem is that Europa is the only world in the solar system that's not ours to explore. As the monolith said: "All these worlds are yours, except Europa. Attempt no landing there. Use them together. Use them in peace."

The amount of mystery that surrounds Europa is quite impressive... I just watched the sci-fi flick Europa Report, which I found to be quite enjoyable, and found that my interest in this moon has definitely increased as of late. I understand that Mars is a scientifically interesting place but we need to look elsewhere too for signs of life.

Instead of attempting to drill through the kilometers thick ice, I would imagine going into a cryovolcano would provide a path into the moon's ocean. Granted, it would still be difficult as any probe would have to able to withstand the stresses involved by diving into a water flowing the opposite direction.

The amount of mystery that surrounds Europa is quite impressive... I just watched the sci-fi flick Europa Report, which I found to be quite enjoyable, and found that my interest in this moon has definitely increased as of late. I understand that Mars is a scientifically interesting place but we need to look elsewhere too for signs of life.

Above and beyond that, we need to look elsewhere for resources and places where we can place footholds for humanity.

With that much (?) water ice, we could surely refine quite a bit of fuel and sustain colonies (of course, after we've done sufficient science on that world.)

I love the thought of colonizing Mars, but colonizing Europa would be one heck of an accomplishment for humanity!

I don't think any object in the Solar System fascinates me more than Europa. It's so mysterious and unexpected, so full of promising possibility, and yet so difficult to crack open and peer at its secrets.

At 35, I hope we do manage to peer under its surface in my lifetime. Landing a man on Mars will be an accomplishment that will dwarf the significance of the Moon landings, and I would be proud to be alive for that. But the possibility of discovering life on Europa (or elsewhere) would certainly change our understanding of the universe, and our place in it.

I don't think any object in the Solar System fascinates me more than Europa. It's so mysterious and unexpected, so full of promising possibility, and yet so difficult to crack open and peer at its secrets.

The iPhone? /cackling laughter

In all seriousness, I'm ten years younger but I don't see it being on my lifetime.

Considering Europa is a close neighbor to Io, a volcanic lunar wonderland, I wouldn't be surprised if Europa has an equally active undersea volcanic layer helping to generate warm water currents. That would make it an excellent candidate for potentially finding hydrothermal vent ecosystem under all that ice.

That would also be something that may be more elusive to model without getting under the ice, as the terrain is sculpted by yet unseen factors. A space probe with an ocean mapping package may be in order.

Among the seven largest natural satellites in solar system, Europa comes second after the Moon as my favourite moon there is also Enceladus, a tiny icy satellite of Saturn. Europa and Enceladus need more missions, than mars.

In actuality, we probably don't want to colonize (or visit in person) Europa - since it sits in Jupiter's very powerful van allen belts, the planet experiences very strong radiation at the surface (although this would be of pretty much no issue for a prospective oceangoing extant lifeform below the ice).

With numbers like that, the only jovian moon worth colonizing (unless you enjoy living your entire life buried in rock on Ganymede) would be Callisto, and other than being a ball of rock and ice with a conveniently low gravity it doesn't really have that much going for it. It's probably less interesting than mars for colonization but I guess it would be more interesting than most other larger-than-our-moon-sized bodies in the solar system.

I don't think any object in the Solar System fascinates me more than Europa. It's so mysterious and unexpected, so full of promising possibility, and yet so difficult to crack open and peer at its secrets.

At 35, I hope we do manage to peer under its surface in my lifetime. Landing a man on Mars will be an accomplishment that will dwarf the significance of the Moon landings, and I would be proud to be alive for that. But the possibility of discovering life on Europa (or elsewhere) would certainly change our understanding of the universe, and our place in it.

NASA, save some of that plutonium! We need it to make that ultraheavy probe that will melt its way through the ice to Europa's ocean (leaving a thin data cable in its wake).

I've also put a lot of thought in to Europa, and to be honest I wouldn't trust a cable through kilometres of ice to not be sheared by moving ice, or any other physically tethered option for that matter. I suppose it all depends on what we can discover before such a hypothetical mission, but I wouldn't take the chance with millions/billions of dollars and decades of work (quite literally) on the line.

I don't get the fascination with colonising other moons / planets displayed in this thread. You just crawled out of one gravity well, only to crawl back down another?! There are countless resource rich asteroids that can be hollowed out and spun up to create habitats, or even chained together into orbitals. Without the cost of climbing up and down a gravity well space travel becomes much easier.

The other issue being the ethics of vandalising pristine environments with our colonies and misguided terraforming attempts.

I don't give a rat's ass about colonization of Europa and I'm puzzled why anyone cares about it. Its truly horrible candidate for that.

The reason why I care about Europa is the possibility of life there, and it has nothing to with colonization. Find life under those kilometers of ice, presuming that it didn't come from astroid sharpnel that hit the Earth, and we have two origins of life in one star system. That means that we live in an universe full of life. I can buy the argument that life is extremly rare, but I can't buy the argument that life is extremly rare and just happened twice on our stars satellites. That is THE reason to study Europa.

Now that is interesting! I had to look into many dimensionless ratios, most often of energy, when getting to grips with mantle convection and plate tectonics. I don't think the Rossby number was one of them, and I didn't know it was so close to balance in (Earth's) oceans.

Accepting the model, that Europa's now certifiably global ocean has a Rossby number larger than one would indicate a lot of thermal energy being transferred into (and out of) it. One could hope that hydrothermal vents (HVs) through the ice interfaces to the core would be one source. That would up the likelihood for life, generically since Io provides more sulfuric salts than metal salts and especially since HVs are implied for abiogenesis.

But repetitive dynamical systems have non-zero likelihoods for any part of their phase space, or in more modern words such systems would be fiercely finetuned. It is a rare process that makes only one object with some specific property.

- Astrobiologists have envisioned it as a possibility for a rare pathway.

That is, if many pathways leads to life, the observation that it happened early on Earth has little bearing on the likelihood for life in the bayesian sense.

But if pathways are competing for success, the locally easiest (likely the globally fastest) pathway is likely the one succeeding. Again you need to constrain such a proposal with an unlikely finetuning to reject the simple hypothesis of speedy life means common life.

Specifically, lately hydrothermal bent systems have been implied in the process that resulted in life here. Those are generic occurrences after formation of bodies that are large enough for core formation (round, hydrostatically balanced bodies).

On terrestrials with an external or internal ocean (ice moons) they could kickstart life. (I.e. on Mars the ocean phase may have been 200 Ma right after the late bombardment when for some reason Tharsis let go with massive volcanism, with enough time for life to appear.)

but I can't buy the argument that life is extremly rare and just happened twice on our stars satellites. That is THE reason to study Europa.

I'm not a huge fan of transpermia as a solution to why life was early on Earth. Even less so after recent suggestions that Mars more likely was late to acquire an ocean and could have been seeded from Earth if anything (see above). But it could happen, and at very low likelihood Earth can have seeded ice moons out to Saturn. (I.e. in recent models Saturnian moons have had 1-10 impacts of Earth material since they were accreted.)

So we need to look out for possibilities of common roots. Luckily it isn't impossible, say phylogenies of the preserved ribosome RNA core or the earliest functional protein folds gives signals of inheritance that can carry for billions of years, deeper than evolution of DNA even.

NASA, save some of that plutonium! We need it to make that ultraheavy probe that will melt its way through the ice to Europa's ocean (leaving a thin data cable in its wake).

Yes, let's drop a slug of plutonium into an ocean of unknown chemical properties like corrosiveness.

It is more than one slug in RTGs, but since it is 238Pu it will only stay Pu for a few hundred years. The ocean water is an excellent shield against the alpha particles in the radium series of 238Pu.

What we send to these outer systems is in effect lead, after a few hundred thousand years of low activity. Lead is poisonous to our own neural systems but may be innocuous or even a useful rarity for any extant life in Europa. All in all I would think they would look to the dissolved metals and plastics of any corroding craft as a nutritious boon.

If US no longer have the economical chops to produce 238Pu, US can perhaps buy it from China that either has stockpiled Russian isotopes or produce them themselves. The just launched Chang'e 3 lander has an RTG, obviously, in order to survive and work through the long Moon nights. (The rover must use local heater isotopes like many US martian crafts to survive cold nights, but it works through the days on solar panels.)

I don't get the fascination with colonising other moons / planets displayed in this thread. You just crawled out of one gravity well, only to crawl back down another?! There are countless resource rich asteroids that can be hollowed out and spun up to create habitats, or even chained together into orbitals. Without the cost of climbing up and down a gravity well space travel becomes much easier.

Fascination #1: The explorer's dreamSure, we can probe other worlds as vigorously and thoroughly as we would like. But none of that beats boots on the ground, exploring said foreign world in person.

Fascination #3: Greed Is GoodHaving established human footholds on other worlds allows us unique opportunities to manufacture, buy, sell, and trade various resources and technologies, some of which we may not discover until we leave Earth's gravity well.

The other issue being the ethics of vandalising pristine environments with our colonies and misguided terraforming attempts.

Ethical questions are decided by individuals, not species, not organizations. I'm sure yours are different than mine. If you find colonizing other worlds to be unethical, you don't have to.

Please, feel free to enjoy any previously pristine locale that we've altered with our misguided landscaping (we don't yet have the technology for out-and-out terraforming). The dwelling in which you're currently living fits the bill, but so does the beach, or nearly anywhere else.

I could go off on a tangent about at what point our ethics on a given topic are superceded by the realities of the topic in question, but I won't. I rest my case for now.